1. Field of the Invention
The present invention relates to a battery pack apparatus. In particular, it relates to a battery pack apparatus comprising a battery pack composed of a plurality of rechargeable batteries and a fan supplying a cooling medium through cooling medium passages between the rechargeable batteries to uniformly cool each of the rechargeable batteries.
2. Description of the Related Art
Apparatuses are known in the art wherein a supply space and a discharge space are disposed above and below a battery pack composed of a plurality of rechargeable batteries arranged in parallel and separated by cooling medium passages formed therebetween, and a cooling medium supply device is disposed to supply cooling medium from one end of the supply space (for example, see Japanese Patent Laid-Open Publication No. 2001-167803).
Also, apparatuses are known wherein a battery pack is formed as an integral unit from a plurality of rechargeable batteries in a rectangular shape inclined in a vertical direction in a containing case, and a fan is disposed beside a lower end portion of the battery pack to supply cooling air to a supply space at an upper portion of the battery pack, the air then passing through passages between the rechargeable batteries and through a discharge space at the lower end and finally discharging outside, thereby cooling each of the rechargeable batteries (for example, see Japanese Patent Laid-Open Publication No. 2001-167806).
Apparatuses are also known wherein a plurality of rechargeable batteries are contained inside a case, and a fan having an impeller is disposed at one side of the case, the impeller having an axial length spanning substantially the entire length in the lengthwise direction of the case. In this apparatus, cooling air is forcedly supplied by the fan to each of the rechargeable batteries (for example, see Japanese Patent Laid-Open Publication No. Hei 8-96858).
An apparatus has also been conceived as shown in FIGS. 6A and 6B. An inflow passage 24 for cooling medium is disposed at a lower portion of a battery pack 21 which has a plurality of rechargeable batteries 22 arranged in parallel and separated by cooling medium passages 23 formed therebetween. A discharge space 25 of a relatively large capacity is disposed at an upper portion of the battery pack 21. A discharge device 26 such as a sirocco fan is disposed at a substantially central portion of an upper surface of the discharge space 25.
However, with the configuration disclosed in Japanese Patent Laid-Open Publication No. 2001-167803, each of the cooling medium passages between the rechargeable batteries, depending on which position in the supply space they communicate, a difference occurs in the circulation amount of the cooling medium, and temperature variations occur among the rechargeable batteries.
The configuration disclosed in Japanese Patent Laid-Open Publication No. 2001-167806 provides a solution to this kind of problem. However, to do so it is necessary to locate the battery pack with an inclination, and the installation configuration is thus complicated. Since a fan is disposed at a side of one end in the lengthwise direction of the battery pack, the entire length is undesirably long.
Also, with the configuration shown in FIGS. 6A and 6B, if the height dimension of the discharge space 25, i.e. a distance H from an upper edge of the battery pack 21 to the discharge device 26, is not large enough, it is not possible to equalize the flow amount of cooling medium passing through the cooling medium passages 23 between the respective rechargeable batteries 22, 22. Thus, a compact configuration in the vertical direction cannot be achieved.
As shown in FIG. 7, a configuration was conceived wherein a cross flow fan 35 is disposed facing a discharge space 34 formed at an upper portion of a battery pack 31, the rotational axis of the fan following in the aligning direction of rechargeable batteries 32. However, by making a distance H between an upper edge of the battery pack 31 and the axis of the cross flow fan 35 as small as possible to facilitate a compact configuration in the vertical direction, variations occur in the flow amount of cooling medium in cooling medium passages 33 between the rechargeable batteries 32,32. That is, the flow rate distribution of cooling medium in the discharge space 34, as indicated by the length of the arrows in FIG. 7, is characterized by a large flow rate at an upper area in the direction of movement of an impeller 36 of the cross flow fan 35, i.e. at an area near a stabilizer 37, but as the distance gets farther away the flow rate decreases. As a result, cooling ability of each of the rechargeable batteries 32 varies depending on the location thereof, thereby causing temperature variations. When the rechargeable batteries 32 are made up from a plurality of cells arranged in parallel, variations occur in the battery temperature and in the SOC between the cells, decreasing the life time of the rechargeable batteries 32.